1. Field of the Invention
The present invention relates to a power window apparatus with a function of pinching detection, and in particular it relates to improving means for further improving the reliability of foreign substance pinching detection by setting an activation/cancellation time period in which the pinching detection is not executed in accordance with the presence of a backlash in a motor for lifting/lowering a window or in a window drive mechanism connecting between the window and the motor.
2. Description of the Related Art
There has been a proposed power window apparatus having a pinching detection function to avoid the pinching by stopping or reversing motor drive when a foreign substance is pinched during window lifting by the motor drive as well as, in order to take a corrective action for a backlash of the drive mechanism, having a pulse encoder for generating a pulse signal corresponding to the rotation of the motor, monitoring means for monitoring the rotating speed of the motor using the output pulse from the pulse encoder during the lifting of the window, pinch recognizing means for recognizing the pinching when the relative reduction in motor revolution exceeds a predetermined determination reference during the lifting of the window, and determination reference changing means for increasing the predetermined determination reference for duration of a predetermined rotating speed since the lifting start of the window after lowering (see Japanese Unexamined Patent Application Publication No. H07-113375).
In this power window apparatus with the pinching detection function, the value of the pinching determination reference for duration of a predetermined rotating speed since the lifting start of the window after lowering is increased by the determination reference changing means, so that the phenomena, in which at the initial lifting of the window after the inversion from the lowering, the rotating motor speed is stably lowered after the high-speed rotation with nearly no-load due to the backlash of the drive system of the window by the motor, is difficult to be misconceived as pinching generation. As this apparatus does not prohibit the pinching determination also during the increasing the pinching determination reference, the pinching prevention can be functioned.
In addition to the above mentioned technique, a power window apparatus with a pinching detection function has also been proposed in that during a predetermined period from the motor start up to the stabilized point of the motor rotation, the pinching is not determined as an activation/cancellation time period.
The size in backlash of a drive mechanism is different for every vehicle due to accuracies in manufacturing of the window drive mechanism with the motor and assembling in the vehicle, and it changes with time. Furthermore, when the window is inverted from the lowering to the lifting, the backlash is large, and when it is lifted again after the lifting, the backlash is small.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. H07-113375, the value of the pinching determination reference for duration of a predetermined rotating speed since the lifting start of the window is increased, wherein “the duration of a predetermined rotation speed” is a period predetermined for each power window apparatus and “the determination reference” is a fixed value selected from values ranging 1.5 to 4 times as long as a normal determination reference. As mentioned above, since there are variations in size of the backlash for each vehicle, “the duration of a predetermined rotation speed” and “the determination reference” have to correspond to the upper limit of the backlash distribution. Accordingly, “the duration of a predetermined rotation speed” may be a considerable long period and “the determination reference” must be a very large value. As a result, although the pinching can be determined directly after the door glass inversion, its reliability is low and the duration is long. In this conventional technique, only in the door glass inversion from lowering to the lifting, the corrective action is uniformly taken; however, there may be cases where the backlash is small in the inversion from lowering to the lifting or the backlash is large when the door glass is again lifted after lifting.
Also, in the power window apparatus with the pinching detection function in that during a predetermined period from the motor start up to the stabilized point of the motor rotation, the pinching is not determined as an activation/cancellation time period, there is also a problem of the long activation/cancellation time period.
When a drive system for elevating a window has a backlash with a size of more than a predetermined value, if the window is lifted after lowering, the motor is rotated at a high speed with nearly no-load, and then the motor rotation speed is stabilized with the starting of the drive system, and as shown in FIG. 11A, the motor rotation speed has a peak value after the motor starting. A time T1 from the motor starting to the peak changes with the backlash size while a time T2 from the peak to a stabilized point P is scarcely affected by the backlash size and does not vary widely, so that the time T2 can be obtained in advance with an experiment or a simulation. Accordingly, when an activation/cancellation time period T is established by the value obtained by adding the time T2 obtained with the experiment or the simulation to the detected time T1, the activation/cancellation time period can be optimized in accordance with the backlash included in the drive system so as to eliminate the above-mentioned inconvenience.
However, when an elastic modulus of the door including a damper in a motor 2 is large, the motor rotating speed does not have a waveform as shown in FIG. 11A, but has a shape having a plurality of peaks as shown in FIG. 11B (two in the example shown in FIG. 11B). In such a shape having a plurality of peaks, the activation/cancellation time period T cannot be optimized by simply adding the time T1 to the time T2 in the case of one peak, so that the reduction in motor rotating speed due to the door vibration may be misconceived as the pinching. In the above-description, the detection of the changes in motor rotating speed has been exemplified; alternatively, when the activation/cancellation time period T is established by detecting a window lifting force applied to the motor, the same inconvenience occurs. The inventors of this application have learned these facts from the researches.
When the window is ill-fitted to a window frame of the door, a clearance is produced between the window and its drive system during vibration of the window in multi-directions so that the motor rotates at high-speed with nearly no-load so as to form a shape with a plurality of peaks in the same way as mentioned above and shown in FIG. 11B. Moreover, it is understood that the difference between the plurality of peaks is small as shown in FIG. 8.